Where is p useful with printf

Question

After all  both these statements do the same thing     int a   10  int  b    amp a  printf   p n  b   printf   08X n  b     For example  with different addresses    0012FEE0 0012FEE0   It is trivial to format the pointer as desired with  x  so is there some good use of the  p option

User · Answer

x is used to print t pointer argument in hexadecimal   A typical address when printed using  x would look like bfffc6e4 and the sane address printed using  p would be 0xbfffc6e4

User · Answer

When you need to debug  use printf with  p option is really helpful  You see 0x0 when you have a NULL value

User · Answer

They do not do the same thing  The latter printf statement interprets b as an unsigned int  which is wrong  as b is a pointer   Pointers and unsigned ints are not always the same size  so these are not interchangeable  When they aren t the same size  an increasingly common case  as 64-bit CPUs and operating systems become more common    x will only print half of the address  On a Mac  and probably some other systems   that will ruin the address  the output will be wrong   Always use  p for pointers

User · Answer

The size of the pointer may be something different than that of int  Also an implementation could produce better than simple hex value representation of the address when you use  p

User · Answer

At least on one system that is not very uncommon  they do not print the same     src gt  uname -m i686   src gt  gcc -v Using built-in specs  Target  i686-pc-linux-gnu  some output snipped  gcc version 4 1 2  Gentoo 4 1 2    src gt  gcc -o printfptr printfptr c   src gt    printfptr 0xbf8ce99c bf8ce99c   Notice how the pointer version adds a 0x prefix  for instance  Always use  p since it knows about the size of pointers  and how to best represent them as text

User · Answer

x is Unsigned hexadecimal integer   32 Bit    p is Pointer address  See printf on the C   Reference  Even if both of them would write the same  I would use  p to print a pointer

User · Answer

You cannot depend on  p displaying a 0x prefix  On Visual C    it does not  Use   p to be portable

[c++] Where is `%p` useful with printf?

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